A variety of sensors exist for monitoring the operation of machinery. These sensors are commonly employed as part of a maintenance program to detect signals corresponding to operation of the machinery for further analysis. For example, sensors are commonly used to detect vibrations emitted by the machinery during operation for further analysis to detect a potential anomaly. Common vibration sensors may employ accelerometers to measure acceleration in sonic frequency ranges for analysis of commonly experienced machine dynamics, or to measure acceleration in ultrasonic frequency ranges for analysis of stress waves, leaks, friction and the like to examine evidence of normal or abnormal events in equipment and machinery that initiate such high frequency vibration signals. For example ultrasonic measurements are commonly used to detect evidence of compressor valve leaks, compressed air leaks and steam trap and valve leaks, air infiltration, electrical emissions, pneumatic operation, actuator operation, pressure and vacuum leak detection (tubes in boilers, heat exchangers, condensers, chillers, distillation columns, vacuum furnaces, specialty gas systems), hydraulic valve bypass, steam trap or other valve testing (leaking or clogged), reciprocating machinery valve blow-by monitoring, compressor valve analysis, pump cavitation monitoring, bearing testing/trending (such as for motors, pumps), gear and gear box inspection, general mechanical inspection, tanks and pipe system testing (integrity of seals and gaskets), cockpit window leaks, wind noise and water leak detection, hatch/marine leak inspection, electrical inspection (anomalies in switchgear), crusher and screen monitoring, flow/no flow/solid flow detection, electrical (arcing/tracking/corona), bearing lubrication failure (fatigue failure, flooding of or lack of lubricant).
Of particular interest is an application of ultrasonic acceleration measurement of fluidborne vibration signals projected from a circumscribed area selected on a gas compressor valve cover. The interest is to observe ultrasonic frequency vibrations indicative of a valve operation, a valve discharge leakage, a valve suction leakage, a ring leakage, a plugging, a worn rider mechanism, other mechanical defects, as well as normal operations of mechanisms and of processes as those skilled in the art are able to understand and interpret from ultrasonic signals produced by fluidborne sensors engaged in sensory contact with the selected circumscribed area. State of the art for measuring and interpreting such measurements is summarized in “Monitoring Reciprocating Compressors 0915”, presented to the Vibration Institute Piedmont Chapter, Sep. 18, 2015 by Mary Chapman, Windrock, a Dover Corporation. A state of the art sensor device reported therein is pictured on slide titled, “UltraSonics to Identify Mechanical Defects” and this sensor device is lacks removable attachment and must be held in place with hand held force. Typical sensors are permanently or semi-permanently attached to a surface of the machinery to detect vibrations in the machinery. These sensors require installation of the sensor on the machinery, such as using a threaded fastener attached to a surface of the machinery. Such installation limits placement of the sensor and requires modification of the outer surface of the machinery to accept installation of the sensor, such as by installing a mounting base on a surface of the machinery. While some sensors allow for detection of vibration of a piece of machinery by contact, such sensors may reduce an effectiveness of the sensor in detecting vibrations and result in increased noise relative to desired signals detected by the sensor.
Magnet mount sonic or ultrasonic frequency range accelerometer sensors are commonly used for removable attachment to ferromagnetic machines. For example, the Model RS1 available from SDT (sdtultrasound.com/products-solutions/solutions/valve-condition-monitoring) threaded ultrasonic sensor with magnetic attachment mounts directly on an object such as a valve cover for hands-free testing. These magnet mount acceleration sensors in the art are responsive primarily to vibrations passed through metal members that provide a connected vibration signal path from a machine surface to sensor detector surface. A complaint often raised with reference to magnet mount sensors from the art has been unwanted signal losses component-to-component linkages. To address that complaint Robinson in U.S. Pat. Nos. 6,435,902 and 6,598,479 teaches an integral magnet mounting configuration. These removable attachment techniques from the art are useful for receiving mechanically transmitted vibrations from a ferromagnetic surface with little discrimination; they are not insulated or isolated from unwanted ambient vibration signals, whether structure borne or fluidborne (gas fluid or liquid fluid).
What is needed, therefore, is a sensor device having a detector of fluidborne vibrations within a probe cavity, a removable hands-free attachment for connecting the free-standing sensor device to a vibrating surface of interest, an isolation boundary surrounding the probe cavity including the detector and sealing an area of interest to the vibrating surface of interest, and a fluidborne vibration coupling medium within the probe cavity for transmitting vibrations or interest from the vibrating surface.